Electric switch



Jan. l5, 1929.

J. D. HlLLlARD ELECTRIC SWITCH Filed NOV. 23. 1922 Inventor:

John )2).Hilli`evr`ol7 b9 M j #His Attceg.

Patented Jan. 15, 1929.

UNITED STATES PATENT OFFICE.

JOHN D. HILLIARD, F SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELCTRIC COMPANY, A CORPORATION GF NEW YORK.

ELECTRIC SWITCH.

Applicatonled November 23, 1922. Serial No. 602,701.

My invention relates to electric switches y and especially to switches which have their contacts immersed in an insulating fluid.

In the operation of fluid break switches, the arc drawn between the switch contacts upon their separat-ion produces intense local heating of the insulatingliquid surrounding the arc path thereby disassociating more or less of this liquid to form a highly heated gas or vapor which suddenly creates a high pressure within the tank, and forms an explosive mixture if permitted access to the atmosphere.` Y

An object of my invention is to provide improved means for absorbing the sudden pressure generated within the insulating liquid upon the separation of the switch contacts. Y Y

A further object of my invention is to provide means for preventing explosions within the switch tank, and for maintaining an inert gas in contact with the surface of the insulating liquid at a pressure designed to prevent. the leakage of air' into the tank.

Other objects and advantages will become apparent as my invention-is consideredin connection with the accompanying drawing, the single figure of which shows, partly in elevation and partly in section, a switch in which one form of my invention has been embodied.

Referring now tothe drawing, the-re is shown a` tank 1, having an insulating lining 2, adapted to contain an insulating liquid 3, the normal level of which is indicated by the shading. A cover 4 is secured to the tank l and is made tightl by the gasket 5. Apertures in the ycover 4'are provided to receive insulating bushings 6 for stationary electrodes A7 the bushings being held in place by the flanges 8, which may be semi-circular in form. Suitable gaskets may be placed between t-he insulators 6 and the flanges 8 in order to make a gas tight connection. The operating rod 10 enters the tank 1 through an aperture 11 in the cover 4 and supports a movable contact bridging member 12. A gas shield 13 adapted to be placed between the tank 1 and its insulating lining 2 is formed integral with the cover 4 and extends below the level of the fluid 3. Another gas shield 14 is attached to the cover 4 around the operating rod 10. A safety valve 15 is inserted in the cover 4 to relieve excessypressure in the tank 1.

y A gas holder 20 rating chamber `by a pipe 21 provided with a valve 22. The gas holder comprises a receptacle 23 formed with concentric vertical walls 24 and 25 between which the is connected to the sepa- Y depending wall of a movable top member f.

26 extends into a sealing liquid designed to prevent the escape of gas from the tank 20. An adjustable counterweight 27 is attached to the cover member 26 in the manner shown to regulate the pressure of the gas within the cock 29 is opened and as the top member rises a mixture of carbon dioxide and nitrogen is drawn into the holder 20.

Fluid may be admitted to the tank through the valve 33 and pipe connection 31. A gas and oil separating chamber casing 16 is connected to the cover by the valved connection 17 Vand is drained into the tank 1 by the pipe 18 in which the check valve 19 is inserted.

An auxiliary expansion chamber casing 30 is located near the bottom of the tank 1 and is provided with a. valved gas drain pipe 31 which is rotatable within the Vopening in the wall of the tank 1 so as to adjust the height of the mouth of the tube 34 in the expansion chamber. Inert gas may be admitted to chamber 30 through the pipe 31 and valve 32.

The switch is prepared for service in the following manner: After the usual contact adjustments have been made the tank 1 is secured to the cover 4 which as is usual in this type of switch is secured t-o a framework or other support (not shown) and the gaskets are then tested for leakage. The tank 1, the separating chamber 16 and the valved connections 17, 18 and 21 are completely filled with the insulating liquid (as evinced by the appearance of liquid flowing out through the valve 35 located at the bottom of connection 21). The proper valves are t-hen manipulated to connect the separating chamber 16 and tank 1 with the gas holder 20 in which has been accumulated a suficient amount of inert gas to replace the excessive insulating liquid. The liquid is then withdrawn `from the tank throughthe pipe 33 to the normal operating level, the space above the liquid being taken up with the gas supplied from the gas holder 20. Pressure upon the gas in the, switch tank 1 is maintained by adjustment of the counterweight 27 which is attached to the top of the gas holder 20. lIhis pressure is preferably somewhat above atmosphericA pressure. Leakage of gas from the system is thus replaced by injecting additional gas into the tank. This is necessary in order to prevent the entrance of air in case of a leak in the tank.

The air entrapped in the auxiliary expan sion chamber 30 may be removed through the Valve 38.' The space originally occupied by this air may then be filled by pumping inert gas into this chamber through the valve 32 under pressure sufcient to overcome the hydrostatic head of the liquid and gas above the chamber in the tank. Accidental dischargeof gas from the auxiliary chamber may be prevented after space in 30 has been filled with gas by rotating the connection 34 until its inner end is free of the chamber.

When the switch contacts are'opened under load, an arc is drawn in the liquid and presu sure is created in the tank by the formation of gas. This pressure is prevented from injuring the tankby forcing part of the liquid into the auxiliary expansion chamber to compress the gas entrapped therein and also by forcing some of the gas above the liquid in the tank back into the gas holder. Should any of the liquid be forced out of the tank by the internal pressure, said liquid will collect in the separating chamber and return to The check the tank via the drain pipe 18. valve 19 prevents liquid from being forced into the separating cham-ber through the drain pipe. Excessive internal pressure in the tank will be relieved by the opening of the safety valve. Secondary explosions in the tank are prevented by reason of the fact that the space above the liquid level. is filled with a gas incapable of supporting combustion.

. My invention may be embodied in other forms than that shown and described and I,

therefore, intend to cover by the appended claims all changes and modifications apparent to those skilled in the artand within the scope of my invention.

lVhat I claim as new and desire to secure by Letters Patent of the United States, is,-

1. In switching apparatus, a.- tan-k Vcontaining a liquid, contacts separable within said liquid to break a circuit whereby an arc is formed and pressure is created within said tank, means forming a submerged chamber arranged beneath said contacts and means for supplying an inert gas to said chamber.

2. In a. switching apparatus, atank containing a liquid, contacts separable within said liquid to break a'circuit whereby an arc is formed and pressure is created Within said tank, means forming a gas compression chamber immersed in the liquid and spaced from the walls of the tank and Vmeans for conveying gas to and from said chamber to regulate the volume of gas therein;

3. In a switching apparatus, a tank consure is created within saidA tank, and a liquid and gas separating chamber communicating with said tank above the normal level of said liquid.

4. In a switching apparatus, a tank containing an insulating liquid and an inert gas, a liquid and gas separating chamber in communication with said tank above the normal level of said liquid, and means for conducting liquid fromA said chamber to said tank.

5. In a switching apparatus, a vessel containing an insulating fluid and an inert gas, a. liquid and gas separating chamber in communication with said vessel, and a pressure tank in communication with said chamber.

6. In a switching apparatus, a tank containing an insulating liquid and anV inert gas, contacts separable within said liquid to break a. circuit whereby an arc is formed and pressure is generated within said tank, means forming a compression chamber beneath said liquid, liquid land gas separating means in communication with said tank, and a source of inert gas under pressure in communication with said separating means. Y

In witness whereof, I have hereunto set my hand this 22nd day of November, 1922. 

